55. Pinnularia nodosa, W. Sm. Valve with three subequal inflations;
extremities subcapitate, produced; striæ marginal, 18 iu
•001". Length ot' valve -0018" to -0025". Breadth at inflations
•0004" to -0005". v.v.
Navícula nodosa, Ehr. Inf. xiii. 9. Kûtz. Bacill. xxviii. 81. Greg. Mic. Journ.
vol. 4. pl. i. 5.
Fresh water. Elchies, Bamffshire, August 1854, Prof. Kelland. (Puy du
Capucni, Mont Dore, elev. 4567 feet, June 1855, W. Sm.)
56. Pinnularia interrupta. Synop. xix. 184.
Var. ft. Costæ not interrupted, v.v.
Pinnularia biceps, Greg. Mic. Journ. vol. 4. pl. i. 28.
Freshwater. New Forest, Hampshire, September 1854 ; Co. Cork, frequent,
&c., W. Sm. Fell-end, Lancashire, August 1854, Mr. Johnson Haverfordwest,
July 1855, Mr. Okeden.
The absence or presence of the costæ at the centre of the valve appears to
be an accidental circumstance, as numerous frustules may be found in which
the interruption is more or less complete. I cannot therefore at present admit
Dr. Gregory’s new species P. biceps, tbe specific name of which is still further
inadmissible, having been appropriated to a very different form, viz. Navicula
biceps, Ehr.
57. Pinnularia integra, TV. Sm. Valve elliptical-lanceolate, with
a slight subterminal constriction and linear produced apices ; striæ
indistinct, 36 in -OOi". Length of valve -0008". Greatest breadth
of valve •0004". v.s.
Pinnularia rostrata, Greg. Mic. Journ. vol. 4. pl. i. 14.
Fresh water. Powmouth, Ayrshire, July 1854, Br. Arnott.
Owing apparently to a central and transverse inflation of the frustule, the
striæ are more distinct and distant at the middle portion of the valve.
The necessity of avoiding confusion in the synonymy of genera so closely
allied as Navicula and Pinnularia, and the appropriation of the specific name
rostrata to Navicula rostrata, Ehr. in Kiitz. Bacill. iii. 55, necessitate the
rejection of an appellation otherwise appropriate and descriptive. The term
integra is designed to imply, that the appearance of a stauros, when the ends
of the valve are out of focus, is deceptive, and that the striæ are truly continuous
over the entire length of the valve.
58. Pleurosigma transversale, TV. Sm. Valve on S. V. elliptical-
lanceolate; extremities obtuse, occasionally slightly produced;
striæ 45 in -001". Length of valve -0032" to -0044". Breadth of
valve -0006" to ’0007". v.v.
Gyrosigma transversale. Micrographie Dictionary, May 1854, pl. xi. 37, 38.
Pleurosigma Naviculaceum, Bréb. Diat. Cherb. fig. 7.
Marine. Stomach of Pecten, Coast of Sussex, February 1853 and March
1854; Kinsale Harbour, April 1855, &c., W.Sm. Stomach of Mytilus,
Coast of Devonshire, Mr. B ’Alguen, March 1854 ; Plymouth, January 1854,
Dr. Arnott. Thames mud, March 1854, Mr. Roper. Milford Haven, April
1854, Mr. Okeden. Lyme Regis, Dorsetshire, 8 fathoms, November 1855,
Mr. Capron,
The present species affects deep water, and seems plentifully diffused along
the British coasts. Its outline is that of a Navicula ; but no one familiar with
these organisms will hesitate to place it with the sigmoid forms of the Pleuro-
sigmata, to which the position of its median line and the structure of its valve
manifestly ally it.
The alliterative blunder in the name Gyrosigma must be my excuse for not
adopting it as the designation of this division of the Naviculaceoe, an excuse
whose validity I find thus admitted by M. De Brébisson in the brochure above
quoted ;—“ Gyrosigma, Hassall. Peut-être ce dernier nom de genre n’était-il
pas bien convenable selon les lois de la nomenclature ; dans tous les cas, il est
certain que, malgré son droit de priorité, il est à peu près généralement abandonné,
comme cela arrive promptement pour les puissances déchues. D’ailleurs,
on est d’autant moins disposé à reprocher ce changement de nom à M. Mb
Smith, que le soin tout monographique qu’il a apporté à l’étude des nombreuses
espèces de Pleurosigma qu’il a découvertes, en fait un genre tout
à lui.”
59. Synedra undulata, Bail. F. V. linear-truncate, arcuate; V.
linear-arcuate, inflated at the centre and towards the rounded
extremities; margins undulated; nodule obsolete; striæ- moniliform,
24 in -001". Length of F. -0134" to -0166". Breadth of V.
at centre -00033"; at extremities -00025"; at the intermediate
points -00017". v.v.
Bail. MSS. et specim. Synedra undulans, Greg. Mic. Journ. vol. 3. pl. iv. 23.
Toxarium undulatum, Bail. Mic. Organ, figs. 24, 25.
Marine. Cork Harbour : attached to Polysiphonia nigrescens, dredged in
depth of 5 fathoms, July and October 1855, W.Sm. Near Lyme Regis,
Dorsetshire, in 8 fathoms, November 1855, Mr. Capron.
This beautiful and curious species was first determined as British by Dr.
Gregory, who found portions of its valves in a sandy deposit from the vallev
of Glenshira near Inverary, and subsequently a single fragment of a valve in a
gatliering I made in Poole Bay in 1849. The specimens I afterwards col-
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